Centralized traffic controlling system for railroads



May 3, 1938. 2,116,177

CENTRALIZED TRAFFIC CONTIiOLLING SYSTEM FOR RAILROADS N. p. PRESTON 3 Sheets-Sheet 1 Filed Aug. 24, 1935 May 3, 1938. N. D. PRESTON 2,

CENTRALIZEOTRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Aug. 24, 1935 s Sheets-Sheet 2 E Fla-.2.

. INVENTOR Mum Patented May 3, 1938 V t UNITED STATES PATENT OFFICE,

GENTR-ALIZED' TRAFFIC CONTROLLING SYSTEM FOR RAAILBJOADS Neil D. Preston, Rochester, N. Y., assig-nor to General Railway Signal Company, Rochester, N. Y.

Application August 24, 1935, Serial No. 37,742

4 Claims. (01. 177-353) This invention relates to centralized traflic confor registering the code character of the control" trol systems for railroads, and more particularly impulses which is reliable in its operation but to a means for registering controls in a communidoes not require the use of additional decoding cation system of the multiple impulse or code means. 7 type. Generally speaking; and by way of explanation In the multiple impulse or code type communiand without attempting to define the nature or cation system commonly employed in centralized scope of the present invention, it is proposed to trafiic control systems for the purpose of governemploy neutral stick control relays directly reing the operation of switches and signals at a sponding in succession to the code character of 10 distant field station from a central control office, the control impulses for thesuccessive' steps, these the controls for governing the operation of the relays individually or jointly controlling the opswitches and signals are transmitted by a series eration of the switches and signals and to conof time spaced plus or minus impulses, or imtrol the stick circuits foreach: of these' neutral pulses otherwise distinguishable in character by stick control relays so as" to be temporarilybroken "variable line circuit conditions or the like. These while an energizing or pick-up circuit for such distinctive control impulses are employed to conrelay is opened or closed dependent upon the dition suitable relays at the field location govcontrol impulse being transmitted, said stick cirerning the operation of power-operated track cuits maintaining the control relay energized at switches and the indications of their associated other times to maintain the desired control efsignals. fective.

In one arrangement, such as disclosed for ex- Other characteristic features, attributes, and ample inthe prior application of Preston and advantages of the organization of relays and cir- Hitchcock, Ser. No. 455,304, filed May 24, 1930, cuits'constituting the present invention will be corresponding to the British Patent No. 377,971, in part apparent, and in part pointed out, as the the character of the control impulse for each step description progresses. or time interval is registered by operating a two The present invention relates to only a part position polarized relay to one position or the of a complete system of code communication for other, the armature of said relay, conveniently centralized traffic control; and while it is contermed a mag-stick relay, being magnetically temple-ted that the invention will be used with held in; the position to which it is set until the various features commonly employed or suitchanged by some subsequent impulse. In such able for such a complete communication sysan arrangement, a control impulse to operate tem, such as station selection, transmission of the mag-stick relay from its existing condition indications, and the like, in order to simplify the to another desired condition may not be eifecdisclosure and explanation of the present inven- 5 tive,. due' to a broken wire or bad contact, or the tion, such features of the complete system are 35 like, with the result that the desired control acnot illustrated and will not be described, except tually transmitted and received at the field locain a general way and in so far as appears to be tionis not properly registered; and while the necessary to understand the functions and mode system for controlling the switches and signals of operation of the parts and circuits constitutisso organized that nounsafe condition is p-roing this particular improvement. 40 duced by such failure, trains may be signalled to In the accompanying drawings, Fig. 1 illustrates advance over a wrong route not desired by the diagrammatically and with various conventional operator. illustrations, one form of this invention; Fig. 2

In another arrangement for registering conillustrates one typical arrangement of circuits trols, neutral decoding relays, all de-energized at for operating the stepping relays; Fig. 3 is a dia- 46 the beginning of a transmitting cycle, are selecgram or chart showing, for explanatory purtively energized in. accordance with the control poses, the sequence of operation of certain relays code transmitted, and then the relays controlling particularly pertinent to an understanding of the the switches. and signals are conditioned, propresent improvement; Fig; 4 shows how the orvidedthe decoding relays have properly respondganization of Fig. 1 may be used in a multiple 5o edto the control code transmitted. This arrangecontrol station system with station selection; and ment requires decoding relays, usually two for Fig. 5 shows a modified organization. each step, in addition to the switch and signal For the purpose of simplifying the illustration control relays. and facilitating the explanation, the various re- One object of this invention is to provide means lays and circuits have been shown diagrammati- 55 cally and conventionally, and the symbols and are employed to indicate connections to the opposite terminals of a battery or other suitable source of current for energizing the circuits, instead of showing all of the wiring connections that would be employed in practice.

Referring to the drawings, the central control ofiice of this system is indicated by a dotted rectangle in the upper left-hand corner of Fig. 1. The code transmitting and receiving equipment in this control office is connected to the equipment at the various field stations by three line wires, comprising a stepping and control line wire SOL, an indication line wire IL, and a common return line wire CL. The stepping and control line wire SCL, together with the common return wire CL, constitute a stepping and control line circuit which is energized in the control oflice with a series of impulses of a selected polarity for operating stepping relays at the field location sequentially one at a time, and conditioning control relays for governing the operation of switches, signals, and the like. For the purpose of explaining and understanding the present improvement, it is considered unnecessary to illustrate the code transmitting equipment in the control office by which these series of impulses are applied to the stepping and control line circuit, first in accordance with the code call for a particular control station to be selected, and then in accordance with the position of switch and signal levers manually set by the operator for the purpose of controlling the operation of corresponding switch machines and signals.

It is contemplated that the controls for a power-operated switch or switches and associated signals will be transmitted as a group to each of the various control stations, one station at a time as the operator positions the switch and signal levers for these control stations and actuates corresponding starting buttons, in the manner disclosed for example in the application of Preston and Hitchcock, Ser. No. 455,304, May 24, 1930 or T. J. Judge and C. S. Bushnell, Ser. No. 640,062, filed October 28, 1932. These applications correspond respectively to British Patent No. 377,971 and U. S. Patent No. 2,082,544. It is also contemplated that the controls for a plurality of switches or for various routes may be transmitted, either simultaneously during the same operating cycle, or successively on different operating cycles, as best adapted to the particular track layout. For the purpose of explaining the nature of the present invention, the various Ways of communicating controls to several control stations for various track layouts may be disregarded, and it is sufficient to consider this invention as applied to a single switch and its associated signals at one field location.

Disregarding the transmission of indications, station selection, arrangement and grouping of switch and signal controls, and other features characteristic of a complete system, incorporating the present improvement, and considering this improvement as embodied in its simplest form, the field station equipment as shown in Fig. 1 comprises a three-position biased to neutral polar line relay F in the stepping and control line SCL; a neutral repeater line relay FP energized each time the line relay F is energized by closure of contact 8, irrespective of the polarity of such energization; a slow-release relay SA picked up at the beginning of each operating cycle and maintained picked up during such cycle even though the line relay F and its repeater FP are only intermittently energized closing contact 9 for each impulse to energize relay SA; a group or bank of stepping relays IV, 2V, etc., including a half-step relay VP; neutral stick control relays WN and WR governing the operation of the switch machine, and similar relays RD and LD for governing the clearing of the associated signals; and a special additional relay X for governing the stick circuits of the control relays WN, WR, etc.

Any suitable arrangement of stepping relays may be employed; and the particular stepping bank illustrated in Fig. 2, and corresponding to that disclosed in the prior application of T. J. Judge and C. S. Bushnell, Ser. No. 640,062, filed October 28, 1932, is merely typical. Since the circuit organization and mode of operation of this bank of stepping relays is explained in detail in said Judge and Bushnell application, and in its specific form constitutes no part of the present invention, it will be sufiicient to point out generally certain characteristic features in the operation of this stepping bank.

During the conditioning period at the beginning of an operating cycle, relays F and FF are energized, and thereafter the relay SA, whereupon relay VP is picked up over a circuit that may be readily traced from through front contact Ill of relay SA, front contact II of relay FP, back contacts I2, l3 and I4 of the stepping relays 3V, 2V and I, relay VP to Relay VP is maintained energized by a stick circuit through its contact I5 and back contacts of the stepping relays. When the line circuit is broken at the end of the conditioning period and relays F and FP are de-energized, the first stepping relay IV is energized by a circuit readily traced in Fig. 2 from through a front contact I6 of relay SA, back contact I! of relay FP, front contact I8 I of relay VP, and back contact I9 of relay 2V, said first stepping relay IV, when energized, being maintained energized through its own front contact 20 and a stick bus 2| and front contact I6 of relay SA until the end of the operating cycle. While relay FF is de-energized, relay VP is held up by a stick circuit through back contact II of relay FP and front contact 22 of relay VP. When the line circuit is again energized, relay VP drops, I

relay IV being now up. During the next de-energization of the line circuit, the next stepping relay 2V is energized through back contact I8 of relay VP, back contact 23 of 3V, and front contact 24 of IV; and during the next following energization of the line circuit, relay VP again picks up to prepare the energizing circuit for the next stepping relay 3V. The same operation is repeated for as many steps as desired.

Thus, in accordance with the particular arrangement of stepping relays assumed for the specific embodiment of the invention illustrated in Fig. 1, after relay VP is initially energized during the first energization of the line circuit in the conditioning period, a stepping relay picks up during each succeeding ole-energization or off period, and the relay VP shifts, i. e., changes from its energized or de-energized condition as the case may be, during each of the succeeding energization or on periods.

This operation of the stepping relays IV, 2V, and 3V establishes sequentially local channel circuits for energizing the control relays WN, WR, RD and LD in accordance with the polarity of energization of the line relay F, during the next on" period following the off period during which the corresponding stepping relay was en-= ergized. l y

Referring to the control relay WN as typical, this relay is energized through its upper winding the relay WN being assumed to be plus to .set the polar contact of relay F to the right; This energizingcircuit may be traced from polar contact .25 of relay F to the right, back contacts 26 and 21 of stepping relays -3V and 2V, front contact, 28 of relay 1 V, through the upper windin of relay WN to Each control relay has a plurality of stick-circuits for maintaining it energized, if energized, underldifferent conditions. One of these stick circuits through the slower winding includes a back contact of the corresponding stepping relay, this stick circuit in the casecf relay WN being 'readily traced from-(-1 through back contact All of the control relays also have stickcircuits through their upper windings connected to a stick bus 32 which is energized through back contacts 33 and 34 of relays FF and SA and front contact 35 of relay X in multiple.

Each control relay,except the one controlled on the last step, has a stick circuit through its lower winding including a front contact of the stepping relay next succeeding thestepping relay controlling the energization of such control relay. In the case of control relay WN, this supple mental stickcircuit may betraced from through front contact 36 of stepping relay 2V, front contact 31 of relay WN, and lower winding of relay WN to Considering now the sequence of operation, and

referring to-Fig. 3 for explanatory purposes,as

sume that the last switch control code was plus to energize relay WN and cause the switch machine to assume its normalp-osition, and suppose that the operator sets the switchlever to the reverse position and initiates the operation of the system. During'the conditioning period,re-

lays F, FP, SA, and VP are energized, and-when relays F and FF are dc-energized, following this conditioning period, the first. stepping relay IV is energized. This breaks the stick circuit for relays WN and WR through the back contact '30 winding. When the line circuit is again closed and energized with a minus polarity corresponding to the switch lever in the reverse position as assumed, the energizing circuit for relay WN is not closed, sincethe polar contact 25. of the line relay F moves to the left; but a similarLpick-up circuit for energizing the-relay WR is established. When the line relay repeater relay FP picks .up and opens its back contact 33, the stick bus 32 is de-energized and the relay WN releases its armature.

It can be seen that when the liriecircuit is opened, after transmission ofthis control impulse,

the line relay F assumes its de-energized condition and opens the energizing or pick-up circuit for relays WN or WR, as the case may be, before the line "repeater relay FP closes its back contact to energize the stick bus 32; and in order to maintain energized the control relay that was energized by the control impulse, relay Xrandits energizing circuit controlled by relay VP and the stepping relays l V, 2V, etcsare provided. Rememberi-ngthat during the energization of the line circuit for conditioning relays WN or'WR, relay V]? is .de-energized, it can be seen that an energizing circuit for relay X is established from (4-),

through b ack contacts 40, 4 I of the stepping relays 3V and 2V, front contact 42 of relay IV, back contact 43 of relay VP,'.and relay X to This energization of :relay X supplies currentto the stick bus 32', and holds up relayWN or WR, as the case may be, during the time the energizing circuit for one or the other of these relays is" broken at the polar contact 25 of the line relay Funtil line relay repeater FP closes its back contact 33. Relay X is not energized until relay VP hasoperated following energization of relay PP, and during this time relayWN or WR-previously energized will have time'to release its armature.

contacts of relay VP and the stepping relays is to provide an additional relay operating time duringwhich the control relay, such as WN may release its armature; and in this respect, the use'of such a'relay X is optional.

Following the energization period during which the control relay WN or WR is conditioned, in accordance with the polarity of such energization, as just described, the opening of the line circuit and de-energization of relays F and FF cause energization of the next steppingrelay 2V, which closes through its front contact 36 the supplemental stick circuitto hold up WN or WR until the end of the cycle. Relay 2V also opens at its back contact 4| the energizing circuit 'for relay X and causes this relay to release its armature preparatory to the control of another control relay, such as RD, during the next succeeding energization period. t

This'same operation is repeated for as manysteps as desired; and in the same manner as described a pair of control relays, suchas WN or WR, may be selectivelyconditioned on each step in accordance with the polarity'of energizetion of the steppingand control line circuit. In the particular arrangement illustrated, the signal control relay RD is energized by a positive impulse on the second step, and the signal control relay LD by a positive impulse on the third step. a This arrangement is merely illustrative of how a single relay may be energized or not on a particular'step depending upon the polarity of the control impulse. 1 Y

The circuits governed by control relays, such as WN and WE, are preferably organized inaccordance with this invention, so that a'relay of each pair-for opposite or conflicting conditions must be energized whilethe other is de-energized in order to produce a controlling conditioii there being no control exercised if both of these relays are either energized or file-energized. For eX-' ample, in the particular arrangement illustrated, the' switch machineSM is'assumed to be constructedto respond to the polarity of energization of its control Wires N and B, being providedwitha polarized master relay :as disclosed, for'example, in the patent to W. K. Howe, No.-

With such an arrangement, if the control relay WNis energized and the other controlrelay WR. is de-energized, the control circuit for the'switch 1,975,135, granted October 2, 1934.

machine is energized with one polarityior-the normalposition through contacts 46 and of In this connection, it may be' stated that the purpose of using the relay X, rather than energizing the stick bus 32 directly through the these relays, and if relay WR is energized while relay WN is de-energized, the switch machine control circuit is energized with the opposite polarity for the reverse position; but if both relays WN and WR are either energized or de-energized, the switch machine control circuit is not energized and the switch machine remains in its existing condition.

The signal clearing circuits are similarly controlled by contacts on the control relays RD and LD; and these signal clearing circuits are also controlled by the switch control relays WN and WR in opposite conditions, so that no signal clearing circuit is established, if both relays WN and WR, or both relays RD and LD, are either energized or tie-energized. For example, taking the signal clearing circuit for signal IA as typical, this circuit may be traced from through back contact 48 of relay LD, front contact 49 of relay RD, front contact 50 of relay WN, back contact 5| of relay WR, and thence through contacts (not shown) of a suitable point detector or switch position relay closed only if the switch points are over and locked m the corresponding normal position, with such other control of the clearing of the signal in accordance with traffic conditions, as may be desirable in accordance with the common practice in signalling systems of this character, such control of the signals in accordance with the positions of the switch point and the like being omitted.

In the particular arrangement shown, the pickup and stick circuits for the signal control relays LD and RD include a front contact 52 of the detector track relay T, in multiple with a back contact 53 of the slow-release repeater TP of this track relay, in the manner characteristic of the disclosure in other prior applications, such as R. F. Wells, Ser. No. 634,370, filed September 22, I932, so that the passage of a train de-energizes the relay LD or RD to cause the signals to assume the stop condition and remain at stop until cleared by some subsequent code, while permitting energization of these relays by a signal clearing code while the detector track circuit is occupied. Either signal control relay LD or RD, if energized to clear a signal, may be de-energized by the operator by sending a control code having an impulse on the respective steps controlling relays RD and LD of a polarity which does not close the energizing circuits for these relays.

From the foregoing it can be seen that, in accordance with this invention, the control relays governing the switch machines and signals at a field location are directly responsive to the character of the successive code impulses, and are selectively energized or de-energized successively as the impulses of the control code are transmitted, so that no additional decoding relays are required to register the control code step by step as transmitted prior to the conditioning of the switch and signal control relays. Even though the control relays are thus directly controlled, each control relay is positively rendered dependent upon the character of the corresponding control impulse, because it is a neutral relay and assumes its deenergized condition when its stick circuits are broken, unless an energizing or pick-up circuit is established. If such energizing or maintaining circuit for any control relay is not established on account of broken wires or bad contacts, such control relay assumes its de-energized or noncontrolling condition, rather than remaining in the condition where last put. Consequently, circuitfailures produce an inactive or non-controlling condition of the field equipment, rather than some controlling condition different from that transmitted.

Also, in accordance with this improvement, the pick-up or sustaining circuit for each control relay is established before its stick circuits are broken, so that a control relay does not release its armature even temporarily if the same control code is repeated. This feature is desirable, particularly in connection with the signal control relays RD and LD, because a temporary de-energization of one of these relays upon a repetition of the same signal clearing code might give a stop indication to confuse the engineer of an approaching train, particularly if color light signals are used.

In the organization of Fig. 1, just described, it is assumed that the desired controls are transmitted on each operating cycle for governing the control relays WN, WR, RD and LD illustrated, but in applying this invention to a multiple station system of the so-called duplex type, such as disclosed for example, in the application of Preston and Hitchcock, Ser. No. 455,304, filed May 24, 1930, there are conditions under which the field station apparatus, including the stepping relays, operates at a time when the proper controls for covering the control relays WN, WR, etc. are not applied to the stepping and control line circuit. Under such circumstances, it is necessary to provide means for holding the control relays WN, WR, etc. in their existing condition, except when controls are being transmitted to the particular control station in question; and such an arrangement is illustrated in Fig. 4.

Referring to Fig. 4, it is contemplated that a relay or relays, such as the relay S0, is energized when controls are being transmitted to the particular control station for governing the control relays WN, WR, etc. The specific type of station selecting or identification means is not material to the present invention; and the station selecting relay S0 for out-bound controls shown in Fig. 4, which is assumed to be governed in the manner disclosed in the above mentioned Preston and Hitchcock application, Ser. No. 455,304, is merely typical.

Assuming such a suitable station selecting or identifying relay SO as shown in Fig. 4, the stick bus 32 for the control relay WN, WR, etc. is energized through a back contact 55 of this relay SO, and is connected to the bus wire 32 extending to the contacts 33, 34 and 35 of the relays FP, SA, and X. Also, the energizing 'circuits for the control relays WN, WR, etc. through the polar contact 25 of the line relay F includes the'front contact 55 of the relay SO. During the station selecting steps, during which the con tinued energization of relay S0 is determined, control relay WN or WR, as the case may be, is maintained energized by its stick circuit through the back contact of the stepping relay aV, corresponding to stepping relay IV of Fig. 1. Control relays RD and LD, and such others as may be employed, are similarly maintained energized by the stick circuits through the back contacts of the corresponding stepping relays bV, cV, and the like. If the control station in question is not called to receive new controls, relay S0 is de-energized when the stepping relays aV, bV, etc. are operated, and the control relays WN and WR are maintained in their existing condition by their stick circuits energized from the stick bus 32, and no current is supplied to their energizing circuits since the front contact 550i relay S is open. When the station is called to receive new controls, however, relay SOis energized at the time the stepping relay (W and the others for the control steps are energized; and under these conditions current is supplied to the polar contact 25 of the line relay F, and the energizationof the stick bus 32 is controlled by relays FP, SA, and X, so that the control relays WN, WR, etc. are setor conditioned in accordance with the control code in the same manner already described.

Fig. illustrates a modification in which the line relay F and the stepping relays aV, bV, etc. are equipped with special make-before-break or continuity contacts in such away as to simplify the circuit organization as illustrated in Fig. 1. The"arniature 60 of the line relay F pivoted at its center, and biased by a spring 6| to the intermediate de-energized position shown, is rocked and moves a contact driver 62 to the right or left, dependent upon the polarity of energization. Spring contact fingers 63, 64 are alternately shifted fromthe position shown to a dotted line position by the driver 62 as the line relay is energized with current of opposite polarity, and open and close contacts suitably constructed, as indicated diagrammatically, to be make-beforebreak. Other contact fingers 65 supply current to the line relay repeater FP whenever the line relay F is energized with current of either polarity. The control relays WN, WR, and such others as rnay be used, have pick-up or energizing circuits through their lower windings, which are supplied with current through the contact fingers 6'3 and 64, with relay SO energized and its front contact 66 closed, when the polar line relay F is energized, in substantially the same way as shown in Fig. 1. The energizing circuit for WN, for example, may be traced from (-1-) front contact 65 of relay SO, wire 61, contact finger 63 in the energized dotted position, wire 69, back contacts Ill and II of stepping relays 0V and 12V,

front contact 12 of stepping relay aV, lower winding of relay WN to- The two control relays for each step, such as WN and WR, have stick circuits including a back contact, as 13, of the corresponding stepping relay; and this contact of the stepping relay has a make-before-break front contact connected to a stick bus 14. When the station is not being called and relay S0 is de-energized, this stick bus 74 is permanently energized through the back contact 66 of the relay SO. When the station is being called, this stick bus is energized through the front contact 66 of relay SO, wire 61, contact finger B3 of relay F in the de-energized position, wire 68, and contact finger B4 in the de-energized position.

Considering the operation of this modification shown in Fig. 5, assume that relay WN is energized, and that an impulse of opposite polarity is transmitted to the particular station in question on step aV for the purpose of de-energizing relay WN and energizing relay WR. During the de-energization period of the line circuit next preceding the control impulse in question, the stepping relay aV is energized, breaking at its back contact 13 the stick circuit for WN, but simultaneously connecting this stick circuit to the stick bus 14, which at this time is energized through contacts of the line relay F and front contact 66 of relay SO. When the impulse of the selected polarity in question is applied to the line circuit and line relay F is energized, its contact finger 64 moves to the left in the case assumed,

these front and back contacts.

establishing an energizing circuit for relay WR,

and at the same time interrupting the supply of current to the stick bus 13. Relay WN then releases its armature, its stick circuit through its upper winding being broken at the contact 64 of line relay F and the energizing circuit through its lower winding being opened at the contact 63 of said line relay. When line relay Fl assumes its de-energized position, after the transmission of the control impulse in question, its contact finger 64 energizes the stick bus 14 and the stick circuit for relay WR now up, before the energizing circuit for relay WR is broken, clue to the make-before-break construction of thecontacts associated with said contact finger 64. During this de-energ'ization period, the next stepping relay bV is energized, and in this modification the stick circuit for the next preceding step relay aV includes a back contact 15 of the stepping relay bV, so that stepping relay av drops and closes the stick circuit for relay WR at its back contact 73, this stick circuit being closed prior to the interruption of the stick circuit to the stick bus 74, due to the make-bBfore-break construction of This same plan of operation takes place for as many steps as desired.

The modification of Fig. 5 employs make-before-break contacts on the polar line relay and on the stepping relays, so as to obtainthe desired overlapping or continuity of the pick-up and stickcircuits for the control relays, rather than dependent upon the sequence of relay operation as in the arrangement of Fig. 1. modification of Fig. 5 has the various characteristic features and advantages already explained for the arrangement shown in Fig. l, the control relays being set or conditioned, if at all, in accorclance with'the control impulse actuallyr'e ceived, without relying upon the integrity of any circuit, so that broken wires andbad contacts produce a' non-controlling condition, rather than a controlling condition inconsistent with the control received. In this connection, it may be pointed out that in both of the arrangements of Figs. 1 and 5, if the line relay during a given stepping interval should, for any reason, due to line surges or the like, shift its contacts quickly from one position to the other and simulate the condition of conflicting controls, the simultaneous energization of the pair of control relays for that step, such as relays WN and WR by such improper double controls, if this should occur, is a non-controlling condition.

Various adaptations, and modifications may be made in the particular arrangement of devices and circuits shown and described as exemplifying the invention, without departing from the fundamental functions and advantages of the invention; and means for receiving or registering controls in a centralized traffic control system, in accordance with this invention, may be employed in conjunction with various other features of a complete system.

What I claim is:

1. In a remote control system of the multiple impulse or code type, an organization for registering controls transmitted to govern the operation of movable devices comprising, line wires for transmitting a series of code conditions each controllable in character, step-by-step means operable to take one step for each code condition, a pair of neutral control relays associated with a particular step and each having energizing circuits, means for selectively energizing the en- This ergizing circuit for one or the other of said control relays on said particular step dependent upon the character of the code condition for that step, first and second stick circuits for each of said control relays, means for opening said first stick circuits only while said step-by-step means is operated for said particular step, and means for energizing said second stick circuits while said step-by-step means is thus operated for said particular step except for a time while one of said energizing circuits is closed.

' 2. In a remote control system of the character described, line wires energized distinctively to provide code impulses of different characters, a series of stepping relays, means for sequentially energizing said stepping relays one at a time for successive energizations of said line wires irrespective of the character of the impulses, a pair of neutral control relays associated with a particular step, means for energizing said control relays selectively in accordance with the character of the code impulse being transmitted, means for maintaining said control relays energized at all other times except while they are being thus conditioned in accordance with the character of the code impulse then being transmitted, and circuits governing the operation of a movable device closed only if said control relays are in opposite conditions of energization and de-energization.

3. In a remote control system; a stepping and control line circuit selectively energized with a series of positive and/or negative impulses; a polar line relay included in said line circuit; a neutral line repeating relay energized each time said polar line relay is energized irrespective of the character of the impulse; a series of stepping relays, means for energizing said stepping relays sequentially, one each time said line repeater relay is deenergized; a pair of control relays for each step; an energizing circuit for each control relay including a front contact of the corresponding stepping relay and a particular polar contact of said polar line relay so that one or the other of a pair of control relays is energized, while their stepping relay is picked up, dependent upon the polarity of the impulse then energizing said polar line relay; stick circuit means for maintaining said control relays energized, if picked up, at all times except a portion of that time while they are being conditioned in accordance with the polarity of the impulse transmitted while their respective stepping relays are picked up; electro-responsive means for each pair of control relays; and circuit means governing the operation of each electro-responsive device closed only if its said pair of control relays are in opposite conditions of energization and d'eenergization.

4. In a communication system of the remote control type; a line circuit having different series of time spaced characteristic impulses transmitted thereover; a line relay included in said line circuit; step-by-step means controlled by said line relay to take one step for each of said impulses; a pair of control relays associated with a particular step; first and second stick circuits for each of said control relays; means controlled by said step-by-step means for opening said first stick circuits during said particular step and at other times closing such stick circuits; means effective while an impulse is being transmitted during said particular step for momentarily opening said second stick circuits; station identifying means rendered effective. only during particular ones of said difierent series of impulses; means controlled by the character of the im'- pulse during said particular step, only if said station identifying means is rendered effective,for selectively energizing one or the other of said control relays during the time that both said first and second stick circuits are opened; and means controlled by said station identifying means, while rendered ineffective, for maintaining said second stick circuits closed.

NEIL D. PRESTON. 

